Gas controlled electrical switch



Aug. 16, 1966 A. SCHONFELD ETAL 3,

GAS CONTROLLED ELECTRICAL SWITCH Filed Aug. 20, 1964 FIG. I

FIG. 2

INVENTORS ARNOLD SCHONFELD JOHN C. SCHULTE ATTORNEYS United States Patent 3,267,230 GAS CONTROLLED ELECTRICAL SWITCH Arnold Schonfeld, Levittown, and John C. Schulte, Maple Glen, Pa., assignors to Sperry. Rand Corporation, New York, N.Y., a corporation of Delaware Filed Aug. 20, 1964, Ser. No. 390,931 1 Claim. (Cl. 200-81.6)

This invention relates to transducers, and more particularly relates to a transducer switch for controlling electric circuits in accordance with gas pressure input signals.

Transducers for modulating or switching an electric current by means of a gas pressure input are known. An example of an air-toelectrical transducer wherein modulation is achieved is a common diaphragm microphone. An example of gas operated electrical switches is the use of a domed snap-action diaphragm linked to a standard electrical switch.

While gas pressure to electrical signal transducers are known as aforesaid, they are often relatively large in size, insensitive or unreliably sensitive, relatively complex, or subject to deleterious aging phenomena which lowers reliability, often without warning. What is needed in miniaturized applications is a transducer for gas-to-electrical signals that is super-sensitive, extremely simple with virtually no moving parts, and virtually oblivious to aging phenomena such as oxidation and the like. While the prior art gas to electrical signal transducers perform the general function, they do not meet these needed qualities.

Accordingly it is a principal object of the present invention to provide a gas pressure to electrical signal transducer that is super-sensitive, and virtually immune to aging phenomena such as wear and oxidation and the like.

Another object of the invention is to provide a device of the character described having extremely high reli ability.

Another object of the invention is to provide a device of the character described that may be made in a greatly miniaturized form without any sacrifice of its other beneficial qualities.

Another object of the invention is to provide a device of the character described which is extremely simple and economical to manufacture.

These and other objects and advantages of the invention will be more fully appreciated and understood upon examination of the hereinbelow contained detailed description of a physical embodiment thereof, when taken with the illustrative figures wherein like reference characters denote like parts in all views thereof and wherein:

FIGURE 1 is a sectioned elevation view of a first embodiment of a gas controlled electrical switch according to the principles of the present invention showing various internal details of construction, and

FIGURE 2 is a section view of the apparatus of FIG- URE 1 taken along line 22 therein.

Referring now to the figures, wherein is shown a presently preferred but merely illustrative embodiment of the inventive principles, a device according to the invention comprises a chamber means defining an enclosed reservoir volume 11, within which volume ll and at the lower portion thereof is located a pool of conductive liquid 12. Preferably chamber means 10 has its outer wall 13 fabricated in a non-electrically conductive gas impervious material suitable for use as hereinafter de- Patented August 16, 1966 portion thereof near the bottom 13a of chamber wall 13. The bore 14a of fine-bore tube 14 is preferably not of a true capillary nature so that liquid 12 may freely ride up and down bore 14a under the influence of a pressure to be presently described. 9 A capillary dimension to bore 14a will also be operable with the present invention but by definition a capillary dimension causes capillary forces that may tend to Work against the gravity action forces which form a part of the action of the present invention as will be hereinafter described. Preferably, on the other hand, the bore 14a has its cross-sectional area kept to a relatively small percentage of the cross-sectional area in the same plane of chamber means 10. Thus bore 14a is preferably, though not necessarily, larger than capillary sized tubing to give free play to gravity forces on any liquid 12 within bore 14a, and on the other hand 14a is kept relatively narrow at least compared to the chamber 10 within which it is situated, so that movement of liquid 12 within it does not appreciably change the level of liquid within the main body of chamber 10, and also so that sloshing or the like within bore 14a is not possible and therefore so that spurious or intermittent contacting (as hereinafter described) is not caused. The term finebore tube will be understood hereinafter to describe a tube 14 satisfying these considerations.

Located above the level of liquid 12, that is within the gas space 11a above liquid 12, is inlet means 16 adapted to communicate with a variable gas pressure source (not shown). Located a distance above the surface 12a of pool 12 is an annular ring 17 afiixed to the inside of wall 13 as is best shown in FIGURE 2. The purpose of annular ring 17 is to prevent undue sloshing of liquid 12 within chamber 10 and yet to allow communication between the surface 12a of liquid 12 and gas space 110. It will be appreciated that annular ring 17 may be increased appreciably in width so as to leave a much smaller annular opening 17a (FIGURE 2) than is presently shown in the figures, while still serving the necessary purpose of allowing communication between gas space 11a and the surface 12a of pool 12. By employment of ring 17 sloshing of liquid 12 upwardly intogas space 11a is virtually eliminated. Ring 17 is however, optional as to use with the invention.

Afiixed to the top portion 13b of wall 13 are two electrical terminals 18 and 19. These terminals are located for convenience, it being possible to locate them at many other places on the exterior of the device. Terminal 18 has a lead-in wire indicated at 18a which for convenience leads from terminal 18 downwardly along the outer wall of tube 14 into the body of liquid pool 12 and to a contact portion 18b conveniently and advantageously located near the very bottom 13a of chamber 10 and near the open end 15 of tube 14. It is only necessary that contact 18b communicate with the body of pool 12, the illustrated location merely being advantageous for coordinated action with open end 15 of tube 14 as hereinafter described. The terminal 19 also has a lead-in wire indicated at 19a which pierces the wall of tube 14 and descends within the bore 14a to a position a predetermined distance above the level of surface 12a where it communicates with a second contact indicated at 1%. A third terminal 21 is a duplicate of terminal 19, and its lead-in wire 20a also pierces tube 14 and terminates in a contact 20b, located somewhat above contact 19b.

Each of inlet means 16, terminals 18,19, and 20, tube 14, and leads 18a, 19a, and 20a, is so disposed with regard to the outer wall 13 of chamber 10, that chamber 10 is gas-tight. That is, none of the recitedintrusions through the wall 13 allows communication between gas space 15 and the ambient atmosphere outside of wall 13. 'Inlet means 16 communicates with gas space 11a, but does not communicate with the ambient atmosphere but rather with the monitored variable gas pressure source (not shown) as aforesaid. The upper end 14b of tube 14 has an orifice 21 therein which communicates between bore 14:: and the ambient atmosphere outside the device. The essential point is thus that the interior of bore 14 communicates at end 21 opposite end 15 with the ambient atmosphere.

By so arranging the parts, a variable gas pressure at inlet means 16 is rendered capable of exerting a variable pressure upon the surface 12a of liquid pool 12. One reason for employing optional annular ring 17 is to prevent cases of sloshing or slight tilting with resultant substantial alteration of the area 12a presented by pool 12 to this variable gas pressure. Assuming for the moment that pool 12 is in the normal position as shown in the figures a certain pressure change thereon will by virtue of the ratio of the area of surface 12a to the ratio of the area of liquid 12b within fine-bore 14a, cause the latter to rise or fall in direct relation thereto. The contact 19b is so arranged Within bore 14a that a predetermined increase in pressure appearing at inlet means 16 will force liquid level 12b up to the level of contact 1% whereupon electrical communication will be established from terminal 19 via lead 19a to contact 19b thence through the portion of liquid body 12 within fine 'bore 14a to the general body of liquid 19 and thus to contact 18b and lead 18a and finally to terminal 18. The contact 20b is located a further distance up the bore 14a so that a further predetermined pressure change is necessary to contact it to the surface 12a. It will be thus observed that a pressure differential at inlet means 16 is capable of controlling, virtually without moving parts, a switching function between contact 18b and contacts 1% and 20b. Wear problems are completely avoided, and if as is preferred gas space 11a is filled with an inert gas such as nitrogen, oxidation problems and other aging phenomena are greatly hindered, and moreover since the various contacts are of the wetted mercury type (when mercury is employed), extended service life is afforded to the contacts themselves.

The arrangement of parts shown in the figures is of course merely illustrative of the principles embodied in the invention. Many changes in the form or specific arrangement thereof can be made while still practicing the inventive principles. For example, the tube 14 need not be vertically disposed within chamber 10. It is merely necessary that one open end of tube 14 communicate with pool 12 and that a second portion of tube 14 situated above the level of pool 12 be normally empty, that is, normally containing gas. Thus slanting tubes 14, or looping tubes 14 or any other configurations satisfying these necessities may be substituted. In all cases of course one contact 18b will be located in communication with the body of liquid pool 12 while at least one contact 19b will be located within the aforesaid normally empty gas space within tube 14. It will be clear however that a plurality of contacts such as 19b and 20b may be employed, or an even greater number. Thus any number of contacts can be arranged along the gas space portion of the tube 14 for separate communication with the liquid at surface 12b as it mounts to various levels in bore 14a. It will thus be appreciated that while the device is very useful as a single pole single throw normally open switch, contacts 19b can be arranged within bore 14a to effect other switching arrangements. -No limitation upon the kind of switching functions which may be performed is to be implied.

In operation, inlet means 16 is attached to a pressure source (not shown) which it is desired to monitor, or in certain circumstances which acts as the control medium for the switch, depending upon the point of view of the use of the device. The normal pressure exerted at inlet means 16 may be taken to be that which causes liquid level at 12b to be as shown in the figures. This would correspond to a normally open switch between contact 18b and each of contacts 19b and 20b. It is of course possible to have the normal pressure at inlet means 16 be such as to hold the level of liquid at 12b at or above the level of contact 19b, or contact 20b. This would correspond to a normally closed switch. In either event when a predetermined pressure change occurs at inlet means 16 the level of liquid at 12b changes in such a manner as to make or break the contact of surface 12b with contact 19b, or with contacts 1% and 20b. It will thus be seen that by variation of the pressure at inlet means 16 a switching function is controlled, and the switching function may be a simple SPST function or other more complex functions depending only upon the arrangement of contacts within bore 14a and the use to which the corresponding external terminals are put. It

is possible to have a plurality of tubes 14, each of which has one or more contacts therein. This can give even further flexibility in switching functions.

While it is preferable to fabricate chamber 10 in a hard impervious non-conductive material such as hard plastic, and while it is preferable to fabricate the tube 14 in glass or plastic, and while as aforesaid it is preferable to employ mercury as liquid 12, clearly other mate-, rials will have the same Working relationship as has already been described between the parts to accomplish the purposes of the invention. Consequently changes in the The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

Apparatus comprising an enclosed chamber made of electrically insulating material containing a pool of electrically conductive liquid in the lower portion of said chamber, a fine-bore tube vertically disposed within the interior of said chamber, the lower end of said tube being open and immersed within said pool of liquid in the lower portion of said chamber such that upon immersion of said lower end of said tube within said pool the interior of the lower portion of said tube is occupied by said liquid, the other upper end of said fine-bore tube extending outside of said chamber, a first electrical contact provided within said chamber in the lower portion thereof and contacting said liquid, at least one electrical contact provided within the interior of said fine-bore tube above said first contact and disposed above the level of said, liquid occupying the lower portion of siad tube, inlet means provided in said chamber for the introduction of a gas thereinto, said inlet means being positioned above the lower end of said tube and above the level of said liquid occupying the lower portion of said chamber and a horizon tally disposed annular ring fixed to the interior of said chamber and positioned intermediate said inlet means and said lower end of said tube, said fine-bore tube passing through a central opening provided in said annular ring.

References Cited by the Examiner UNITED STATES PATENTS 1,106,907 8/1914 Wilkinson 200-81.6 X 2,198,351 4/1940 Thielers et a1. 200152 X BERNARD A. GILHEANY, Primary Examiner.

G. MAIER, Assistant Examiner. 

